Maybe I shouldn't post this topic right here, but I'd like to have an answer to a question I keep asking myself since I know EB (not much, so).
In the sentence "Quisque est barbarus alio", why is it "alio"? I study Latin and, in my opinion and for what I know about this language, this sentence hasn't the meaning you want to give it.

In fact "Everyone is a barbarian to someone" should be "Quisque est barbarus ALII" (Alius,-a,-ud. Dative: Alii).

Of course, I'm sure there's not a mistake (I can't be the first one who's noticed it) so I'd like you to explain me why the sentence is written that way. Besides, I know "alio" instead of "alii" is found in some documents, but it was principally a volgar variation...

Thank you, and sorry for being so pedant